From dad4f5012e6ec9fb45537d607b9e4a0ed8f17203 Mon Sep 17 00:00:00 2001
From: Sam Harwell <Sam.Harwell@microsoft.com>
Date: Thu, 6 Feb 2020 05:32:48 -0800
Subject: [PATCH] Enable VSTHRD103 (Call async methods when in an async method)

---
 .editorconfig                                 |  3 ---
 .../Utilities/ResourceManagerUtils.cs         |  4 ++--
 .../Utilities/TaskExtensions.cs               | 20 +++++++++++++++++++
 .../Microsoft.ML.Sweeper.Tests/TestSweeper.cs | 14 ++++++-------
 4 files changed, 29 insertions(+), 12 deletions(-)
 create mode 100644 src/Microsoft.ML.Core/Utilities/TaskExtensions.cs

diff --git a/.editorconfig b/.editorconfig
index 6b5fc14e6e..0ce9d216c3 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -7,9 +7,6 @@ dotnet_sort_system_directives_first = true
 # VSTHRD002: Avoid problematic synchronous waits
 dotnet_diagnostic.VSTHRD002.severity = none
 
-# VSTHRD103: Call async methods when in an async method
-dotnet_diagnostic.VSTHRD103.severity = none
-
 # VSTHRD200: Use "Async" suffix for async methods
 dotnet_diagnostic.VSTHRD200.severity = none
 
diff --git a/src/Microsoft.ML.Core/Utilities/ResourceManagerUtils.cs b/src/Microsoft.ML.Core/Utilities/ResourceManagerUtils.cs
index 046880b922..f731b12e91 100644
--- a/src/Microsoft.ML.Core/Utilities/ResourceManagerUtils.cs
+++ b/src/Microsoft.ML.Core/Utilities/ResourceManagerUtils.cs
@@ -154,11 +154,11 @@ private async Task<string> DownloadFromUrl(IHostEnvironment env, IChannel ch, st
                 var timeoutTask = Task.Delay(timeout).ContinueWith(task => default(Exception), TaskScheduler.Default);
                 ch.Info($"Downloading {fileName} from {url} to {filePath}");
                 var completedTask = await Task.WhenAny(t, timeoutTask);
-                if (completedTask != t || completedTask.Result != null)
+                if (completedTask != t || completedTask.CompletedResult() != null)
                 {
                     downloadCancel.Cancel();
                     deleteNeeded = true;
-                    return t.Result.Message;
+                    return (await t).Message;
                 }
 
                 return CheckValidDownload(ch, filePath, url, ref deleteNeeded);
diff --git a/src/Microsoft.ML.Core/Utilities/TaskExtensions.cs b/src/Microsoft.ML.Core/Utilities/TaskExtensions.cs
new file mode 100644
index 0000000000..eba5cdb0d7
--- /dev/null
+++ b/src/Microsoft.ML.Core/Utilities/TaskExtensions.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics.CodeAnalysis;
+using System.Threading.Tasks;
+using Microsoft.ML.Runtime;
+
+namespace Microsoft.ML.Internal.Utilities
+{
+    internal static class TaskExtensions
+    {
+        [SuppressMessage("Usage", "VSTHRD002:Avoid problematic synchronous waits", Justification = "The task is completed.")]
+        public static TResult CompletedResult<TResult>(this Task<TResult> task)
+        {
+            Contracts.Check(task.IsCompleted);
+            return task.Result;
+        }
+    }
+}
diff --git a/test/Microsoft.ML.Sweeper.Tests/TestSweeper.cs b/test/Microsoft.ML.Sweeper.Tests/TestSweeper.cs
index c1b20cd6bb..d0c116a80b 100644
--- a/test/Microsoft.ML.Sweeper.Tests/TestSweeper.cs
+++ b/test/Microsoft.ML.Sweeper.Tests/TestSweeper.cs
@@ -206,7 +206,7 @@ public async Task TestDeterministicSweeperAsyncCancellation()
                 if (i < args.BatchSize - args.Relaxation)
                 {
                     Assert.True(task.IsCompleted);
-                    sweeper.Update(task.Result.Id, new RunResult(task.Result.ParameterSet, random.NextDouble(), true));
+                    sweeper.Update(task.CompletedResult().Id, new RunResult(task.CompletedResult().ParameterSet, random.NextDouble(), true));
                     numCompleted++;
                 }
                 else
@@ -218,7 +218,7 @@ public async Task TestDeterministicSweeperAsyncCancellation()
             await Task.WhenAll(tasks);
             foreach (var task in tasks)
             {
-                if (task.Result != null)
+                if (task.CompletedResult() != null)
                     numCompleted++;
             }
             Assert.Equal(args.BatchSize + args.BatchSize, numCompleted);
@@ -254,9 +254,9 @@ public async Task TestDeterministicSweeperAsync()
             {
                 var task = sweeper.Propose();
                 Assert.True(task.IsCompleted);
-                paramSets.Add(task.Result.ParameterSet);
-                var result = new RunResult(task.Result.ParameterSet, random.NextDouble(), true);
-                sweeper.Update(task.Result.Id, result);
+                paramSets.Add(task.CompletedResult().ParameterSet);
+                var result = new RunResult(task.CompletedResult().ParameterSet, random.NextDouble(), true);
+                sweeper.Update(task.CompletedResult().Id, result);
             }
             Assert.Equal(sweeps, paramSets.Count);
             CheckAsyncSweeperResult(paramSets);
@@ -273,9 +273,9 @@ public async Task TestDeterministicSweeperAsync()
                 var task = sweeper.Propose();
                 Assert.True(task.IsCompleted);
                 tasks[i] = task;
-                if (task.Result == null)
+                if (task.CompletedResult() == null)
                     continue;
-                results.Add(new KeyValuePair<int, IRunResult>(task.Result.Id, new RunResult(task.Result.ParameterSet, 0.42, true)));
+                results.Add(new KeyValuePair<int, IRunResult>(task.CompletedResult().Id, new RunResult(task.CompletedResult().ParameterSet, 0.42, true)));
             }
             // Register consumers for the 2nd batch. Those consumers will await until at least one run
             // in the previous batch has been posted to the sweeper.